1. Field of the Invention
The present invention relates to an expansion valve that constitutes a refrigerating cycle, and more specifically, to an expansion valve capable of excluding noise produced therein.
2. Description of the Prior Art
There are various types of expansion valves. In widely used expansion valves, a valving element is opposed from the upper-stream side to an orifice that is formed by constricting the middle of a high-pressure refrigerant passage through which a high-pressure refrigerant is fed into an evaporator. The valving element is opened and closed according to the temperature and pressure of a low-pressure refrigerant that is delivered from the evaporator.
An example of the expansion valves of this type is used in a refrigerating cycle of an automotive air conditioner or the like. As shown in FIG. 10, the refrigerating cycle comprises a refrigerant compressor 2 that is driven by means of an engine, a condenser 3 connected to the discharge side of the refrigerant compressor 2, and a receiver 4 connected to the condenser 3. The refrigerating cycle further comprises an expansion valve 5, which adiabatically expands a liquid refrigerant from the receiver 4 into a vapor-liquid refrigerant, and an evaporator 6 connected to the valve 5.
A valve body 5a of the expansion valve 5 is formed having a high-pressure-side passage 5b into which the liquid refrigerant flows and a low-pressure-side passage 5c through which the vapor-liquid refrigerant flows out. The high- and low-pressure-side passages 5b and 5c communicate with each other by means of an orifice 7. A valve chamber 8d is provided with a valving element 8 for adjusting the flow rate of the refrigerant that passes through the orifice 7.
The expansion valve body 5a is penetrated by a low-pressure refrigerant passage 5d. A plunger 9a is slidably located in the passage 5d. The plunger 9a is driven by means of a temperature sensing drive element 9 that is fixed on the top of the valve body 5a. The drive element 9 is divided into two parts, an upper gastight chamber 9c and a lower gastight chamber 9cxe2x80x2, by a diaphragm 9d. A disc portion 9e on the upper end of the plunger 9a abuts against the diaphragm 9d. A tube fixing hole 9g is formed in the central portion of a top lid 9f of the temperature sensing drive element 9. A capillary tube 9h is attached to the hole 9g.
At the lower part of the expansion valve body 5a, a compression coil spring 8a is located in the valve chamber 8d. The spring 8a causes a support member 8c to press the valving element 8 in the valve-closing direction. The valve chamber 8d is defined by an adjust screw 8b that mates with the valve body 5a and is kept gastight by means of an O-ring 8e. An operating rod 9b abuts against the lower end of the plunger 9a. The rod 9b causes the valving element 8 to move in the valve-opening direction as the plunger 9a slides.
The plunger 9a in the temperature sensing drive element 9 transmits temperature in the low-pressure refrigerant passage 5d to the upper gastight chamber 9c. Pressure in the chamber 9c changes according to this temperature. If the temperature is high, for example, the pressure in the chamber 9c increases, so that the diaphragm 9d presses down the plunger 9a. Thereupon, the valving element 8 moves in the valve-opening direction to increase the flow rate of the refrigerant that passes through the orifice 7, thereby lowering the temperature of the evaporator 6.
If the temperature is low, on the other hand, the pressure in the upper gastight chamber 9c lowers, so that the force of the diaphragm 9d to press down the plunger 9a is reduced, and the valving element 8 is moved in the valve-closing direction by means of the compression coil spring 8a that urges the element 8 in the same direction. Thereupon, the flow rate of the refrigerant that passes through the orifice 7 lowers, and the temperature of the evaporator 6 rises.
Thus, the expansion valve 5 moves the valving element 8 to change the opening area of the orifice 7 according to the temperature change in the low-pressure refrigerant passage 5d, thereby adjusting the temperature of the evaporator 6. In the expansion valve 5 of this type, the opening of the orifice 7, which adiabatically expands the liquid refrigerant into the vapor-liquid refrigerant, is set in a manner such that the spring load of the variable-load compression coil spring 8a, which presses the valving element 8 in the valve-closing direction, is adjusted by means of the adjust screw 8b. 
In the expansion valve 5 shown in FIG. 10, the capillary tube 9h is attached to the tube fixing hole 9g of the temperature sensing drive element 9. FIG. 11 shows another example of the expansion valve 5. In this example, a sealing plug 9i is attached in place of the tube 9h to the hole 9g. The expansion valve body 5a is in the form of a column having a square cross section. Thin-walled portions 5e are formed individually on the opposite sides of the bottom portion of the body 5a, and bolt holes 5f are bored near the low-pressure refrigerant passage 5d. 
The expansion valve 5 shown in FIG. 10 is a temperature-type expansion valve that detects the outlet temperature of the evaporator 6 (temperature of the low-pressure refrigerant passage 5d) and transmits it to the temperature sensing drive element 9 of the valve 5. If the expansion valve of this type is used in a refrigeration system of an air conditioner of an automobile, for example, in general, the automobile is left for a while under relatively high-load conditions related to the outside and inside air temperatures. If the refrigerating cycle (air-cooling operation) is then started, the liquid refrigerant is fed into the evaporator at a high rate, since the opening of the expansion valve is wide. Possibly, therefore, noise may be produced when the refrigerant passes through the expansion valve.
In some cases, moreover, the high-pressure refrigerant that is fed into the expansion valve may be subjected to pressure fluctuation on the upper-stream side in the refrigerating cycle. This pressure fluctuation is transmitted to the valve by the medium of the high-pressure refrigerant. Thereupon, in the expansion valve shown in FIG. 10, the refrigerant may possibly produce noise as it expands. When the pressure fluctuation of the refrigerant on the upper-stream side is transmitted to the valving element, the operation of the valving element may become unstable. In this case, vibration of the valving element may possibly produce noise.
Accordingly, a sound insulating case has been proposed as a measure to tackle the above problems of the prior art (Japanese Patent Application Laid-open No. 2002-29251). It is attached to the outside of an expansion valve lest noise leak out. Since this sound insulating case has a complicated shape, however, its manufacturing cost is high, and its attachment to the expansion valve is very troublesome.
The object of the present invention is to provide an expansion valve, which can be easily fitted with sound insulating members having simple construction and has excellent sound insulating and vibration-proof effects.
According to a first aspect of the invention, there is provided an expansion valve comprising two case members of the same shape attached to an expansion valve body through sound insulating members.
Each case member has retaining portions and retainable portions arranged at the upper and lower parts thereof, the retaining portion of one case member being capable of engaging the retainable portion of the other case member, and the retainable portion of the one case member being capable of engaging the retaining portion of the other case member.
The outer surface of each case member is flat.
According to a second aspect of the invention, there is provided an expansion valve comprising two sound insulating members of the same shape attached to an expansion valve body so as to cover the same.
Each sound insulating member has retaining portions and retainable portions arranged at the upper and lower parts thereof, the retaining portion of one sound insulating member being capable of engaging the retainable portion of the other sound insulating member, and the retainable portion of the one sound insulating member being capable of engaging the retaining portion of the other sound insulating member.
The outer surface of each sound insulating member is flat.
According to a third aspect of the invention, there is provided an expansion valve comprising an expansion valve body having therein a high-pressure-side passage, low-pressure-side passage, and orifice internally connecting the passages, a valving element opposed to the orifice, and a temperature sensing drive element having a diaphragm for driving the valving element by means of an operating rod and being located outside the expansion valve body. The expansion valve further comprises a case member attached to the expansion valve body and the temperature sensing drive element so as to extend along the whole contours thereof except outlets and inlets of the passages in the expansion valve body. The case member includes two members of the same shape in engagement with each other.
The case member is attached to the entire temperature sensing drive element except a part thereof.
The case member is mounted through a sound insulating member.
One of the two members constituting the case member is formed having a retaining portion, and the other member is formed having a retainable portion in a position corresponding to the retaining portion, the case member being attached to the expansion valve body and the temperature sensing drive element with the retaining portion and the retainable portion in engagement with each other.
The retaining portion and the retainable portion are formed inside the case member.
Each of the two members constituting the case member is formed having a retaining portion and a retainable portion, the case member being attached to the expansion valve body and the temperature sensing drive element in a manner such that the retaining portion of one of the members is in engagement with the retainable portion of the other member and that the retainable portion of the one member is in engagement with the retaining portion of the other member.
The retaining portion and the retainable portion are arranged side by side on each member.
According to the invention, moreover, there is provided a sound insulating case of an expansion valve, comprising two sound insulating members of the same shape and two case members of the same shape for holding the sound insulating members.
Constructed in this manner, the expansion valve according to the present invention has the following effects.
Since the two case members of the same shape are attached to the expansion valve body with the sound insulating members between them, sound insulating and vibration-proof effects can be obtained, and besides, it is necessary only that components of the same shape be prepared as the case members. Thus, the manufacturing cost can be lowered, and handling the valve can be facilitated.
Since the two sound insulating members of the same shape are attached to the expansion valve body, sound insulating and vibration-proof effects can be obtained, and besides, the construction can be simplified, and handling can be made easier.
The retaining and retainable portions are formed side by side on the respective upper and lower parts of the case members. Thus, the two members of the same shape can be easily mounted or removed at a stroke in a manner such that the retaining and retainable portions are caused to engage one another when the members are attached to the expansion valve body.
Since the outer surface of each case member or sound insulating member is flat, handling properties, such as the ease of attachment of the expansion valve as a whole, are improved.
Since the two case members of the same shape are attached to the expansion valve body, sound insulating and vibration-proof effects can be obtained, and besides, it is necessary only that components of the same shape be prepared as the case members. Thus, the manufacturing cost can be lowered, handling the valve can be facilitated, and the construction can be simplified. Further, the retaining and retainable portions are formed side by side on the respective upper and lower parts of the case members. Thus, the two members of the same shape can be easily mounted or removed at a stroke in a manner such that the retaining and retainable portions are caused to engage one another when the members are attached to the expansion valve body.
Since the sound insulating case of the expansion valve is composed of the two sound insulating members of the same shape and the two case members of the same shape for holding the sound insulating members, the number of indispensable components can be reduced.